getting invested quickly

The secondary market is indeed hard to navigate. However, Trilight's very useful spreadsheet takes a lot of the pain out of it. You can find this on either forum; he starts new threads each month. The old forum is better because there is more discussion there - including some quite educational stuff this month.

If you are logged in to the old forum, this link should work: www.forum.thincats.net/forums/topic/january-sm/. Threads in the new forum are impossible to link to.

The main drawback with the spreadsheet is that by the time he publishes it (usually daily) one more bargains may have gone. So it is worth looking at the market regularly to see what's new - which will always be at the top.

If you can pick up fixed rate offers on the SM, they will always be at par (= original interest rate), which is actually a discount because you get the accrued interest for free. It can be a good way to get started, if you like the loans on offer. Ignore the displayed "target rate" on fixed rate offers, if it differs from the original rate. This is a bug resulting from cached data not being cleared correctly when fixed rate listing requests are submitted. All fixed rate sales are processed at par.

I'm slowly building up my TC portfolio, but it can be a struggle. I can well imagine 15 months to get up and running.

The primary market goes from feast to famine, and at the minute most of the offerings are interest only (which I try to avoid).

Two possibilities:

1. If you are bidding on a fixed rate auction, then as stated in my previous post you must ignore the displayed "target rate" on fixed rate offers, if it differs from the original rate. This is a bug resulting from cached data not being cleared correctly when fixed rate listing requests are submitted. All fixed rate sales are processed at par. Put simply, if it is a fixed rate auction, you must bid at the original rate.

2. Broadly speaking, the system will only accept bids for a par amount that is either a multiple of £1,000 or the remainder of the loan part on offer. I have seen reports that if you try to do anything different you will get this message.

Also, are you bidding from the Auction Summary page or from the Bid Listing (which you get to by clicking the grey box on the Auction Summary)? Some things seem to work better if you bid from the Bid Listing. Worth a try.

For help with TC problems generally, you are better off posting on one of the TC forums. More TC lenders participate there and you might get some other suggestions.

A few different points here.

Where do I see what the original rate is?
You can see the original rate on the DO Details tab, accessible from the Auction Summary. [Edit: it's captioned Bid Rate.] In this case it is 10.98%. At the moment also appears in brackets in the drop-down box for either a Standard or Dynamic bid. This might change if the auction is filled with bids at a lower rate; I'm not sure.

...avdg and max bids 0 for some reason
"Avg rate" and "Max rate" currently refer to rates of succesful bids in this auction. They are nil because there have been no successful bids. This is unhelpful. Max rate should tell us the maximum permitted rate but at present it does not. You have to guess. I will come back to this... Edit: the maximum permitted rate is there but it is well hidden. Go to the DO Details tab (see above) then click on the tab "DO Auctions" and you will see a screen that includes the maximum rate. This screen is actually one of the older ones in the system but it got buried in one of the updates. In this case it is 10.25%, ie target +0.25%, which is usual.

...I will be ignoring the target rate as per your post
This is a variable rate auction so you should not ignore the target rate. It should be ignored only on fixed rate auctions. The target rate is what the current lender hopes to get but it is usually possible to bid at a slightly higher rate. The maximum permitted rate is set manually by TC. At one time it was usually set 0.25% higher than the target rate, so my first guess as to the maximum permitted rate would be 10.25%, but it could be higher (and you can't bid at 10.25% anyway - see below). Edit: see above.

When I try bidding and entering £1000 manually then the adjusted rate is 10.98% (how is that calculated?)
I infer that you are trying to make a standard bid. The system is showing you the original rate in the adjusted rate box. I don't know why. In any case you will need to change it because, as you have discovered, it will not let you bid at that rate...

I then can't bid at this rate as it tells me 'bid rate not a multiple of bid decrement'.
The standard bid decrement on a SM auction is 0.1%. This used not to restrict the rates at which bids could be made, it just forced dynamic bids to step down in 0.1% steps. However, I have established by trial and error that this auction will only accept bids in whole multiples of 0.1%. It's a while since I bid on a variable rate auction but I think this is a relatively recent change.

Also: why does my bid amount change, when I change the bid rate?
AFAIK the bid amount does not change when you change the bid rate. It certainly should not. What does change is the bid price. You pay a premium if the bid rate is less than the original rate, or a discount if it is more.

I suggest trying a bid at (say) 10.5%. If the system won't accept this it means the max has been set lower. Go down by 0.1% at a time until it is accepted.
Edit: In this case, although the max rate has been set at 10.25%, the max rate at which you will actually able to bid is probably 10.2%.

Also consider making a dynamic bid rather than a standard bid as this puts you at the front of the queue if the rate is bid down. But be sure to set your lower rate at a multiple of 0.1 and don't set it lower than you are prepared to go.

Not at all. Please see the edits to my previous post as I have just discovered where the maximum bid rate is hidden.

This particular auction is showing the original rate on the loan ("Bid Rate") at 13.00% and a Target Rate of 12.00%. The maximum bid has been set at 12.25%, but  we have just established that the system probably won't let you bid at 12.25%.

Try a dynamic bid with an upper rate of 12.2%.

A few words of caution regarding TLCs and the SM.

There are two types of TLC
(1) Vanilla TLCs that pays interest at 7% as they go along. At the end you get any surplus.
(2) Roll-up TLCs where all interest is paid at the end.

The SM software works by reference to the original par value of the loan, which makes it hard (and in the case of roll-up TLCs sometimes impossible) to sell TLC loan parts at a realistic premium - see for example page 2 of the thread General > SM DOs January on the new forum.  There is also some uncertainty about the tax treatment of rolled up interest if they are sold before maturity.

If I were you, I would avoid investing in new roll-up TLCs unless I was sure that I would be able to hold them to maturity. They might be worth buying on SM if you can get get them at a sufficient discount to their net asset value but this is A-level stuff and not really recommended for beginners. You need to know your way around the Dropbox and understand the limitations of the information provided in the TLC progress reports.

This is much less of an issue for vanilla TLCs because the premium bulding up will be much smaller (and could well be zero or negative if there are losses). They are a better buy IMO, if you are happy to leave the loan selection to TC's algorithm.

Finally I would note that recent TLC issues have not been very popular so they are relatively small. This limits their bid size on individual loans so their bids may not be big enough to get cashback.

I usually just try buy anything from 10% interest onwards. I know this is not very sophisticated but I don't really have time to examine each loan and I don't believe I will be able to add value or smell out fishy loans so I try to diversify. Otherwise I am beginning to wonder why not just stick with assetz capital and funding secure. The latter has securitised loans starting from 12% and often you can get a bonus of 2%, so 15% in total; also much easier to navigate and understand what's happening. The reason I also opened an account with thincats is to get invested quickly but actually it is proving one of the slowest platforms so far for me to get invested...
Is there a default statistic for thincats anywhere? I have no idea what I am buying...