What if P60 does not cover entire duration?

Since P60 is issued in April, it doesn't cover full period of my application.
(06 Oct to 07 Sep)

I'll supply 12 payslips, P60 (as stated above 06 Oct to 07 Mar) and bank statements.

Will that suffice?

You can use the bank statement instead. However, P60 is definitely the best.

And also submit a letter from employer describing your salary statement in past 12 months with signed and stamped payslips....all docs should corroborate with each other....hence provide same set of info in all...

Send the P60 (but don't tick the box for tax return in the previous earnings section). Explain that your P60 covers only part of the period and that you have supplied 1. Bank statements and/or 2. Letter from employer in addition to your wage slips. At the end of the application form on the last page, you can tick the box that shows that a tax return (P60) has been included and explain all this in your cover letter. The important thing is that net pay on your wage slips should match 100% the salary on your bank statements. Salary should state where it's coming from and not just "credit" or "salary". Gross earnings on your employer letter should match 100% gross on your payslip.