By Ian Pollock BBC personal finance reporter

Standard Life hopes to raise more than �1bn by selling new shares

The insurance company's shares will start trading next Monday on the stock market.

But current members have until 1000 BST on Wednesday to decide if they want to cash in by selling their windfall shares immediately.

They, along with ordinary customers and staff, must also decide by then if they want to do the opposite and increase their shareholding.

They can do this by subscribing to buy more shares, which are being offered to them with a 5% discount to whatever turns out to be the eventual flotation price on Monday.

Buying

Cliff Freeman, from Northiam in Sussex, gets a pension from a Standard Life policy.

Cliff Freeman hopes to get �5,000 worth of shares

As such he is not eligible for any windfalls as he is not a member.

But he is part of the wider group of customers and staff who can apply for preferential shares with the discount.

He says he has applied for �5,000 worth of them because he wants to enhance his savings.

"I don't know how many I'll get. They may be scaled back and I might get just 10% of the amount I asked for."

Hanging on

One Standard Life member, Mark Hickey from Woodford Green in north-east London, will be getting some windfall shares.

Mark Hickey plans to hang on to his windfalls

He is going to hang on to them but will not buy any more.

"I don't have any immediate need for the cash and I don't think there's any point in selling them while the market is flat," he said.

"Also, no one knows what the value of the shares is yet, so you'd be selling them blind. I'll hang on for a year to get the bonus shares. They may even be worth more if there's a takeover."

That is a point emphasised by independent financial advisor Jonathan Fry.

"The insurance industry has too many players and is very competitive. The chances of a possible takeover do seem high and that would almost inevitably push up share prices," he said.

"The main downside is that it is very difficult to assess the timescale. It might not happen quickly so I'd be cautious about buying more shares."

Bonus shares

People who keep their new shares for 12 months continuously will get bonus shares in a year's time, at a rate one for every 20 they have held.

If the share price were to be unchanged that would be the equivalent of a 5% bonus on the initial holdings.

But financial advisors are pointing out one important wrinkle.

If the shares are put into an individual savings account (ISA) they will forfeit this bonus.

That is because transferring them to an ISA technically involves buying and selling them back, thus undermining the idea that they have been held continuously.

The same applies to shares put into a Self Invested Personal Pension (SIPP) as the shares are in fact sold to the SIPP.

The pricing of the shares by Edinburgh-based Standard Life and its advisors will take place after the stock market closes this Friday.

The debut price for the shares will be announced over the weekend and trading will start on Monday.

Cheques for any windfall shares that have been sold back to Standard Life will be sent out after that and all other documentation should be sent out by 17 July.