Repayments/interest calculated incorrect?

[federalist]

Hi guys! I've been reviewing a car credit agreement I am currently paying, I was originally trying to calculate my own settlement figure using the Actuarial method.

 

However, it seemed to me that in the interest figures stated on the Credit Agreement don't quite add up:

 

The interest rate is 26.98% per annnum, and is fixed for the duratation of this Credit Agreement

APR: 49.9%

Cash Price: £8,200.00

Deposit: £200.00

Amount of Credit: £8,000

Interest: £10,972.00

Arrangement Fee: £250.00

Credit Facility Fee: £195.00

Total Charge for credit: £11,417.00

 

Total Payable: £19,617.00 (ouch!)

Payment setup is as follows:

 

1st Payment of: £250.00 (arrangement fee)

59 payments of: £316.20

Final Payment of: £511.20 (includes credit facility fee)

 

When I calculate the interest due using the 26.98% figure, my total payable is always much less than my agreement says it should be. Who's wrong, me or the agreement? And in any event, what formula is used to calculate interest on this type of finance?

[federalist]

By my calculations, at this rate the loan should be paid off by month 43:

 

Month   Balance   Principal   Interest   Payment       
1    £8,445.00     £60.13       £189.87     £250.00        
2    £8,384.87     £127.68     £188.52     £316.20        
3    £8,257.19     £130.55     £185.65     £316.20        
4    £8,126.64     £133.49     £182.71     £316.20        
5    £7,993.15     £136.49     £179.71     £316.20        
6    £7,856.67     £139.56     £176.64     £316.20        
7    £7,717.11     £142.69     £173.51     £316.20        
8    £7,574.42     £145.90     £170.30     £316.20        
9    £7,428.52     £149.18     £167.02     £316.20        
10   £7,279.33     £152.54     £163.66     £316.20        
11   £7,126.80     £155.97     £160.23     £316.20        
12   £6,970.83     £159.47     £156.73     £316.20        
13   £6,811.36     £163.06     £153.14     £316.20        
14   £6,648.30     £166.72     £149.48     £316.20        
15   £6,481.58     £170.47     £145.73     £316.20        
16   £6,311.10     £174.31     £141.89     £316.20        
17   £6,136.80     £178.22     £137.98     £316.20        
18   £5,958.58     £182.23     £133.97     £316.20        
19   £5,776.34     £186.33     £129.87     £316.20        
20   £5,590.02     £190.52     £125.68     £316.20        
21   £5,399.50     £194.80     £121.40     £316.20        
22   £5,204.70     £199.18     £117.02     £316.20        
23   £5,005.52     £203.66     £112.54     £316.20        
24   £4,801.86     £208.24     £107.96     £316.20        
25   £4,593.62     £212.92     £103.28     £316.20        
26   £4,380.70     £217.71     £98.49     £316.20        
27   £4,162.99     £222.60     £93.60     £316.20        
28   £3,940.39     £227.61     £88.59     £316.20        
29   £3,712.78     £232.72     £83.48     £316.20        
30   £3,480.06     £237.96     £78.24     £316.20        
31   £3,242.10     £243.31     £72.89     £316.20        
32   £2,998.79     £248.78     £67.42     £316.20        
33   £2,750.02     £254.37     £61.83     £316.20        
34   £2,495.65     £260.09     £56.11     £316.20        
35   £2,235.56     £265.94     £50.26     £316.20        
36   £1,969.62     £271.92     £44.28     £316.20        
37   £1,697.70     £278.03     £38.17     £316.20        
38   £1,419.67     £284.28     £31.92     £316.20        
39   £1,135.39     £290.67     £25.53     £316.20        
40   £844.72        £297.21     £18.99     £316.20        
41   £547.51        £303.89     £12.31     £316.20        
42   £243.62        £310.72     £5.48     £316.20        
43  -£67.10         £317.71    -£1.51     £316.20